Lorien E. Urban of Tufts University in Boston and colleagues conducted a study to evaluate the overall accuracy of restaurant-stated calories from 42 restaurants, comprising 269 total food items and 242 unique foods.
The food was analyzed at a laboratory for caloric content. The menu items was randomly selected from fast-food and sit-down restaurants in Massachusetts, Arkansas and Indiana from January to June last year, Urban said.
Of the 269 food items analyzed, 40 percent were off by 10 calories. Nineteen percent contained 100 calories more than stated on the menu. The menu items that were most off were those in sit-down restaurants, as opposed to fast-food restaurants, the study said.
In an analysis of 10 percent of the food items with the highest positive discrepancy, the average difference between measured and stated energy contents was 289 calories, the study said.
"Considering the first and second sampling of the 13 foods together, the 26 foods had a mean (average) measured energy content of 273 calories higher than the stated energy content, representing a 48 percent discrepancy," the study authors said in a statement.
The findings are published in the Journal of the American Medical Association.